The present disclosure relates to a developing device for supplying a developer to an image bearing member and an electrophotographic image forming apparatus including the developing device.
An electrophotographic image forming apparatus irradiates a photosensitive layer constituting a peripheral surface of a photosensitive drum (image bearing member) with light, based on image data obtained through scanning of an original document image or on image data transmitted from an external device such as a computer, to form an electrostatic latent image on the photosensitive drum. A developing device supplies toner to the photosensitive drum on which the electrostatic latent image has been formed to form a toner image. Thereafter, the toner image formed on the photosensitive drum is transferred onto paper (recording medium). The paper onto which the toner image has been transferred is subjected to fixing of the toner image thereon, and then ejected out of the apparatus.
In a known development scheme, a dry toner is used in an image forming apparatus employing an electrophotographic process. The dry toner development scheme uses a two-component developer including a magnetic carrier and a non-magnetic toner. In the two-component developer development scheme, for example, a magnetic roller (toner supplying roller) carries the developer to a development roller that is disposed out of contact with a photosensitive drum (image bearing member). During the above, only the non-magnetic toner is transferred onto the development roller with the magnetic carrier left on the magnetic roller. As a result, a thin layer of toner is formed on the development roller. The non-magnetic toner transferred to the development roller flies to the photosensitive drum due to an alternating electric field in a region where the development roller is opposite to the photosensitive drum (development region). As a result, the electrostatic latent image formed on the photosensitive drum is developed into a toner image.
In recent years, image forming apparatus configuration has become more complicated along with progress toward color printing and high-speed processing. In order to achieve high-speed processing, toner stirring members in developing devices are required to rotate at higher speed. In the above-mentioned two-component developer development scheme, in particular, a magnetic brush is formed on the magnetic roller in a region thereof opposite to the development roller, and the magnetic brush enables only the toner to be transferred onto the development roller. Toner left unused in the development is separated from the development roller. As a result, toner cloud is likely to be generated in or around a region where the development roller is opposite to the magnetic roller. Toner from the toner cloud is accumulated around a bristle cutting blade (controlling blade). The accumulated toner may aggregate and adhere to the development roller to cause an image defect leading to toner peeling.
In order to solve the problem, a developing device includes a flexible sheet member and an elliptical roller that causes swing of the sheet member in a wall portion between the controlling blade and the development region that faces toward the development roller. The sheet member constitutes a portion of an internal surface of the wall section and is swingable in a direction perpendicular to the internal surface of the wall section.
Another development device includes a shaking mechanism that accelerates toner adhering to a wall of the development device in such a direction that the toner is shaken off into a case.
In another development device, a film member is attached to an inner wall portion (sleeve cover) of a developer container disposed opposite to the development roller. While the development roller is rotating, a protrusion formed on an outer circumferential surface of a gear intermittently comes in contact with the film member to oscillate the film member. As a result, toner accumulated on the film member is shaken off.